Girl swallowing aluminium for a fever (7)
I believe the answer is:
malaria
'fever' is the definition.
(I've seen this before)
'girl swallowing aluminium for a' is the wordplay.
'girl' becomes 'mari' (**).
'swallowing' is an insertion indicator.
'aluminium' becomes 'al' ('Al' can be a synonym of 'aluminium').
'for' is a charade indicator (letters next to each other).
'mari' placed around 'al' is 'malari'.
'malari'+'a'='MALARIA'
(Other definitions for malaria that I've seen before include "Illness" , "Mosquito-transmitted disease" , "Disease causing fever transmitted by mosquitos" , "Disease carried by mosquitoes" , "Tropical fever" .)